Soy is one of the least expensive sources of food grade vegetable protein. Soy flour, soy protein isolates, soy grits, soy flakes, soy meal and the like have long been incorporated into foods such as ready to eat and other breakfast cereals, bread formulations, snack products, soup and gravy mixes, meat loaf, protein and carbohydrate containing animal food and the like.
More recently, soy has found increasing use in the preparation of protein food products simulating meat in texture and appearance. For example, U.S. Pat. No. 3,537,859 discloses a process whereby a mixture comprising soy meal, fat and water is extruded to form a porous extrudate resembling bacon in texture and appearance. U.S. Pat. No. 3,488,770 discloses the preparation of expanded soy protein food having the texture of cooked meat when rehydrated. According to U.S. Pat. No. 3,496,858, a fibrous, meat like protein food is prepared by extruding under high pressure a mixture comprising soy meal and minor amounts of sulfur or a sulfur compound.
One of the major disadvantages with the use of soy in human or animal food is the bitter or beany flavor and aroma characteristics of soy. Expanded soy processed with reactants such as sulfur or sulfur compounds has the added disadvantage of slight sulfur odor or off-flavor. Thus, the amount of such soy products that can be incorporated into a given food is limited by the natural or processed soybean flavor; the higher the soy content, the less palatable the food.
There have been many attempts to reduce the disagreeable soy flavor or odor such as by heating soybeans either dry or with steam or by adding materials such as yeast to the soy prior to processing. While some of these techniques are effective to some extent, further improvement is desirable.
It is an object of this invention to prepare a palatable soy food wherein the disagreeable soy flavor and odor is markedly reduced.